The present invention relates in particular to the use of at least one polypeptide to obtain a diagnostic, prognostic, prophylactic or therapeutic composition for for detecting, preventing or treating a pathological condition associated with a degenerative and/or autoimmune and/or neurological disease.
According to the invention, the expression degenerative disease is understood to mean a disease in which a process of cell death or of cell destruction is associated with physiological and/or clinical disorders. Alzheimer's disease, amyotrophic lateral sclerosis and Parkinson's disease are classified amongst neurogenerative diseases. The expression autoimmune disease is understood to mean a hyperactivity of the immune system toward one or more autoantigens. Multiple sclerosis (MS), rheumatoid arthritis (RA) and lupus erythematosus are classified among autoimmune diseases.
Multiple sclerosis is a chronic disease of the central nervous system in humans which progresses through a succession of phases of remission and of flare-up or in a regular progression and whose anatomicopathological characteristic consists in the formation of well delimited demyelination zones in the white substance of the brain and of the spinal cord.
At the histological level, these zones exhibit, at the early stage of the lesional process, a degradation of the periaxonal myelin associated with an impairment of the glial cells responsible for this demyelination.
Inflammatory macrophage activation causing the microglial cells (resident tissue macrophages of the central nervous system), as well as, probably, macrophages from infiltrated blood monocytes, is associated with this demyelination process and contributes to the destruction of the myelinated sheets. At the center of the demyelinated zone, there is a relative depletion of glial cells whereas a proliferation of astrocytes develops at the periphery and can invade the demyelinated plaque in order to generate a fibrous or gliotic plaque. These sclerotic structures are responsible for the name given to the disease.
Another characteristic of these plaques is their almost systematic association with a vascular element around which they develop.
At the histological level, a frequent alteration of the blood-brain barrier (BBB) consisting of capillary endothelium is observed. One of the key elements in maintaining the BBB consists of the underlying presence of cytoplasmic extensions of the astrocytes, called astrocytic feet. Possibly, the astrocytic feet induce the formation or allow the maintenance of tight joining structures which ensure the cohesion of the capillary endothelial barrier concretizing the BBB. However, various pathological models report the alteration of the BBB and a depletion of the astrocytic feet.
Moreover, in the lesional process in MS, the alteration of the BBB contributes toward amplifying the associated inflammatory response by the influx of lymphoid cells from the bloodstream. The contribution of the inflammation associated with the immune cells is important in MS and participates in the lesional process.
The etiology of MS is the source of a current debate because the disease could have various origins. Hypotheses have been emitted on a bacterial and/or viral origin. Moreover, as described in patent application WO 95/21859, H. Perron et al. have been led to investigate one or more effector agents for the pathogenic process resulting in the typical formation of demyelination plaques and in astrocytic gliosis. In the context of this study, they demonstrated the presence, in the cerebrospinal fluid (CSF) and the serum of MS patients, of at least one factor which exhibits a toxic activity toward human or animal astrocyte and oligodendrocyte cells. This toxic activity is characterized by a cytomorphological disorganization of the network of intermediate filaments and/or a degradation of the proteins of said filaments and/or a cell death by apoptosis of the glial cells. They established a significant correlation between the in vitro detection of this toxic activity in samples of CSF and of serum of MS patients and multiple sclerosis by a quantitative calorimetric assay with methyltetrazolium bromide (MTT) of the live cells, as described in patent application WO 95/21859. Moreover, C. Malcus-Vocanson et al. have shown that urine is a very favorable biological fluid for the detection of the activity of this toxic factor and developed a method using flow cytometry to detect and/or quantify the adherent glial cells which are dead through apoptosis. All the information relating to this method is described in patent application WO 98/11439, whose content is incorporated by way of reference.
Trials were carried out starting with a protein fraction of CSF and of urine from MS patients in order to try to identify this toxic factor. The protein content of each fraction was separated on a 12% SDS-PAGE gel and observed after silver staining of the gel. Among the proteins observed, a protein fraction centered over an apparent molecular weight of about 21 kD was found not predominantly associated with the toxic activity detected in vitro and a fraction centered over an apparent molecular weight of about 17 kD was found predominantly associated with the toxic activity.
Injection of the fraction from the SCF of MS patients into the brain of Lewis rats and postmortem histological observation of brain sections of the rats made it possible to observe, three months after the injection, an apoptosis of the astrocytic population and the formation of demyelination plaques. All the information is contained in patent application WO 97/33466, whose content is incorporated by way of reference. These observations are in accordance with those which have been made on the brain sections of patients suffering from MS, after biopsy (N. Benjelloun et al. Cell. Mol. Biol., 1998, 44(4), 579–583).